Fortunguavis xiaotaizicus (Wang, O'Connor and Zhou 2014; Early Cretaceous; IVPP V18631) was described as a robust enantiornithine bird with strongly recurved pedal unguals. Here the elements of the skull are traced and reconstructed for the first time. This taxon nests transitional to ornithurine birds. This is the last time the postorbital connects to the squamosal and jugal in the bird lineage.

Iberomesornis romerali (Sanz and Bonaparte 1992, LH-22, Barremian, Early Cretaceous, 125 mya) tiny bird (8.7 cm axial column) with short wings (20 cm wingspan), and no pygostyle contra the original description.

Cratoavis cearensis (Carvalho et al. 2015a, b; Early Cretaceous, Aptian; UFRJ-DG 031; 6cm long, sans tail feathers). This taxon was originally considered a hummingbird-sized enantiornithine, but nests with Iberomesornis. The tail is transitional from long and unfused to a pygostyle, convergent with other clades that also evolve a pygostyle. Lacking primary feathers, this specimen was likely a nestling, unable to fly.

Longipteryx chaoyangensi (Zhang et al. 2001, Aptian, Early Cretaceous 131 mya; 15cm long) is a transitional enantiornithine at the base of the Hesperornis clade. Note the shorter tibia than femur. Elongate caudals are retained. Mt4 = Mt 3. Gastralia and sternum overlap.

Rapaxavis pani (Morschhauser et al. 2009, O'Connor et al. 2011, DMNH D2522; 10cm long) is a sister to Longipteryx in the LRT. Note the extreme fragility of the rostral bones.

Schizooura lii (Zhou , Zhou and O'Conor 2012; Early Cretaceous) nests between the enantiornithine Rapaxavis and the Euornithes. The excellent preservation permits an accurate reconstruction and scoring. An extremely thin nasal process separates the naris from the antorbital fenestra. The postorbital is large enough to touch the jugal. Distinctly the quadrate curls posterodorsally and the postorbital contacts the squamosal. A short tail without a pygostyle is present. Toe 3 is the longest, as in most birds and theropods, but distinct from closely related taxa.

Carvalho I, Novas F, Agnolín F et al. 2015a. A Mesozoic bird from Gondwana preserving feathers. Nature Communications 6, 7141. https://doi.org/10.1038/ncomms8141

Carvallho I et al. 2015b. A new genus and species of enantiornithine bird from the Early Cretaceous of Brazil. Braz. J. Geol. 2015, vol.45, n.2, pp.161-171. ISSN 2317-4692.  http://dx.doi.org/10.1590/23174889201500020001.

Morschhauser EM, et al. 2009. Anatomy of the Early Cretaceous bird Rapaxavis pani, a new species from Liaoning Province, China. Journal of Vertebrate Paleontology. 29(2): 545–554.

O'Connor JK, Chiappe LM, GAo C-L and Zhao B 2011. Anatomy of the Early Cretaceous enantiornithiine bird Rapaxavis pani. Acta Palaeontologica Polonica, 56(3):463-475.

Sanz JL and Bonaparte JF 1992. A New Order of Birds (Class Aves) from the Lower Cretaceous of Spain. In JJ Becker (ed): Papers in Avian Paleontology Honoring Pierce Brodkorb. Natural History Museum of Los Angeles County Contributions in Science 36:38-49.

Wang M, O'Connor JK and Zhou Z 2014. A new robust enantiornithine bird from the Lower Cretaceous of China with scansorial adaptations. Journal of Vertebrate Paleontology 34(3):657-671.

Zhang F, Zhou Z, Hou L and Gu, G 2001. Early diversification of birds: Evidence from a new opposite bird". Chinese Science Bulletin. 46 (11): 945–949.

Zhou S, Zhou Z-H and O'Conor JK 2012. A new basal beaked ornithurine bird from the lower Ctetaceous of Western Liaoning, China. Vertebrata Palasiatica 50(1):9–24..

wiki/Fortunguavis - not yet posted
wwiki/Iberomesornis
wiki/Cratoavis
wiki/Longipteryx
wiki/Rapaxavis
wiki/Schizooura